1. Field of the Invention
The present invention concerns packet mode radio communications and more particularly the allocation of uplink radio resources in a radio communication system.
2. Description of the Prior Art
The problem arises in radio communication systems of allocating uplink radio resources between the various remote stations, in other words, the problem of managing multiple access. The problem does not arise on the downlink, i.e. in the direction from the gateway to the remote stations. For the uplink, i.e. in the direction from the remote stations to the gateway, it is necessary to arbitrate the use of radio resources between the remote stations.
There are two solutions to this problem. Firstly, multiple access can be managed by detecting collisions. In a protocol of this kind, the remote stations transmit without any synchronization being required and an information bit is transmitted correctly only if only one remote station transmits at a time. This type of protocol can be validly based only on a shared radio resource that is low in cost because its capacity is greatly increased compared to what is strictly necessary.
Access from the remote stations to the common radio resource can also be synchronized by a function which assigns multiple access requests (DAMAxe2x80x94dynamic allocation multiple access). This type of protocol is described by Argagnon C. et al. in xe2x80x9cANIS or providing multimedia services via satellites, though effective use of standardsxe2x80x9d, IAF""98, Melbourne, for example.
U.S. Pat. No. 5,327,432 also addresses the problem of allocating time slots to remote stations of a time-division multiple access radio communication system. The solution proposed in this prior art document is for the gateway to transmit an allocation message which is processed in a remote station by a message-segmenting circuit. This prior art document is more particularly concerned with the time slot allocation protocol.
U.S. Pat. No. 5,363,374 describes an anticipatory method of allocating resources. To reduce the time needed to allocate resources, this prior art document proposes transmitting the resource reservation request before the total number of resources required is known.
Document EP 0.484.387 describes a method which entails maintaining an up-to-date list in a gateway of remote stations which are currently requesting transmission of packets of a given type and a given length. The gateway determines which remote stations are to be allocated time slots and transmits a frame which indicates the slots allocated for transmitting packets in the next frame. The slots allocated are defined by the respective positions in the frame of the identifiers of the remote stations that will be authorized to transmit.
The object of the invention is to improve on the above prior art methods.
To be more precise, the invention proposes a method of allocating uplink radio resources in a time-division multiple access packet mode radio communication system comprising at least one gateway and a plurality of remote stations each of which comprises means for storing packets to be transmitted, the method including the steps of:
storing packets to be transmitted from a remote station in a plurality of queues,
referring to the identifiers of the queues of a remote station in the transmit authorizations for each time slot of a frame,
during one frame, transmission by a gateway of transmit authorizations for a next frame which include the identity of a remote station authorized to transmit during said slot and which are written in at least one table in each remote station, and
during the next frame, reading of the transmit authorizations in the table by each remote station and transmitting packets stored by each remote station as a function of the transmit authorizations read in this way.
The invention also proposes a remote station of a multiple access packet mode radio communication system for implementing the above method.
Other features and advantages of the invention will become apparent on reading the following description of one embodiment of the invention which is given by way of example and with reference to the accompanying drawing.